Rhododendron Propagation and Pruning

Hi all,
I am very keen on Rhododendrons and need some advice on the best way to develop new plants. I know that one it can be done by air layering and simple layering but are there easier ways, eg a greenwood/semi-ripe cutting or by seeds? If I can do cuttings, when should I take them.

I currently have 2 plants in pots. Should I start feeding them liquid ericaceous plant food now or wait a month?

I have heard that I should prune them after flowering, is this correct, as there are a couple of stems with no growth on that I would like to take back to the main stem to improve it's appearance.

I have also read that you should gently pull off the flower head when it is spent to prevent seed production and to assist with greater flowering for next season, is this correct?

Any help would be greatly appreciated as these are the jewels in my crown!

Ian
South West London

On Tue, 22 Feb 2005 14:38:48 +0000, KingstonIan
wrote:


Hi all,
I am very keen on Rhododendrons and need some advice on the
best way to develop new plants. I know that one it can be done by air
layering and simple layering but are there easier ways, eg a
greenwood/semi-ripe cutting or by seeds? If I can do cuttings, when
should I take them.

I currently have 2 plants in pots. Should I start feeding them liquid
ericaceous plant food now or wait a month?

I have heard that I should prune them after flowering, is this correct,
as there are a couple of stems with no growth on that I would like to
take back to the main stem to improve it's appearance.

I have also read that you should gently pull off the flower head when
it is spent to prevent seed production and to assist with greater
flowering for next season, is this correct?

Any help would be greatly appreciated as these are the jewels in my
crown!

Rhodies can be grown from cuttings, but it's not easy, and I've never
done it. The cutting material should be semi-ripe wood, taken in late
summer, say August. Select shoots from the current year's growth, and
trim them to about 7 cm long. You don't have to have a 'heel', but try
and cut the lower end at a node. Remove the lower leaves, leaving only
three or four surrounding the terminal bud. Use hormone rooting powder
if you think it helps. The potting mixture should be very free
draining, say equal parts of peat and coarse grit or fine gravel. Use
7 cm pots, and make sure they can also drain freely, e.g. stand on
gravel. You can either use a cold frame against a north-facing wall,
or put pots singly in polythene bags and seal them. What it important
is that they should never be allowed to wilt, so keep them out of
direct sun. They will take several months if you're lucky. Bottom heat
and a misting unit help no-end.

But an easier and probably more reliable, if slower, method for the
amateur without a heated mist unit is layering, which I gather you
know about.

You can also grow them from seed, but unless you are skilled at
pollination there is a risk that insects will subsequently contaminate
your efforts with pollen from other rhodies nearby. Nor will self-
pollinated hybrids necessarily come true, AIUI, however careful you
are, but I'm no expert on genetics. Seed from 'open pollinated'
flowers won't necessarily come true either, due to pollination from
neighboring plants. I once germinated and grew on, seed from R.
yakushimanum when it was scarce and expensive. I got a surprising
range of hybrids, all nice, as well as some true yakushimanums. There
must have been some R. orbiculare near the parent plant, as several of
the offspring resembled it.

As for pruning, if you're doing it just to tidy up the shape a bit
then there's seldom any problem. But if you're planning some heavy
size reduction, I've found that some rhodies come again vigorously
while others give up and die. Unfortunately I don't know which does
which! As you say, do it after flowering, but I don't think it's too
crucial if you're just tidying it.

Removing the flower heads when they're over, stops the plant putting a
lot of energy into setting seed, and encourages flowers next year, as
you say. But it's not essential, and on large specimens, almost
impossible. I'm sure they don't do much dead-heading in the big
National Trust gardens. The technique is to hold the whole flower
truss near its base with finger and thumb, with the remains of the
flowers and stamens enclosed in your hand, and twist and pull
together. But you must take care not to remove or damage the young
shoots which are emerging from just behind the truss. If you're not
sure what these are, postpone your dead heading until these shoots are
clearly visible. Whilest you can now see them easily, the bigger they
are the easier it is to knock them off accidentally. It's not a
disaster if you do though. There are lots of dormant buds below the
flower truss, and more will start to grow, but it does delay things.

Incidentally, a couple of feeds with sulphate of ammonia (1 dessert
spoon per 2 gallon can) during April and June do wonders for growth,
and a feed with a similar amount of potassium sulphate towards the end
of July will encourage flower-bud set in late summer and early autumn,
ready for next spring. Mulch in spring with leafmould or coarse peat
to keep the roots cool, and water every week in dry weather.


--
Chris

E-mail: christopher[dot]hogg[at]virgin[dot]net

I'll start with layering........thankyou very much for your help.

Regards,

Ian